Frequency Offset Correction in a Software Defined HiperLAN/2 Demodulator using Preamble Section A

In our Software Defined Radio project we perform a feasibility study of a software defined radio for two communication standards: HiperLAN/2 and Bluetooth. In this paper the Matlab/Simulink implementation of the HiperLAN/2 demodulator for the demonstrator of the project is discussed, with special attention for the frequency offset corrector. This type of correction is necessary to prevent large bit error rates that are caused by inter-subcarrier interference. The method that is proposed in this paper uses preamble section A to estimate the frequency offset. Simulation results for an AWGN channel show that the method is capable of correcting frequency offsets up to the boundary defined in the standard [1]. It was observed that frequency offset correction using only preamble section A is sensitive to ¿for example¿ synchronization errors in case real-life analog front-end signals are used

There is no number effect in the licensing of negative polarity items:a reply to Guerzoni and Sharvit

Guerzoni and Sharvit (Linguistics and Philosophy 30:361-391, 2007) provide an argument that plural, but not singular, wh-phrases may contain a negative polarity item in their restriction, and connect this with the semantic property of exhaustivity. I will show that this claim is factually incorrect, and that the theory of negative polarity licensing does not need to be complicated by taking number distinctions into account. In addition, I will argue that number distinctions do not appear to be relevant for polarity items in the restriction of definite noun phrases either

The origin of the warped heliospheric current sheet

The warped heliospheric current sheet in early 1976 was calculated from the observed photospheric magnetic field using a potential field method. Comparisons with measurements of the interplanetary magnetic field polarity in early 1976 obtained at several locations in the heliosphere at Helios 1, Helios 2, Pioneer 11 and Earth show a rather detailed agreement between the computed current sheet and the observations. It appears that the large scale structure of the warped heliospheric current sheet is determined by the structure of the photospheric magnetic field, and that "ballerina skirt" effects may add small scale ripples

Reversals of the solar magnetic dipole in the light of observational data and simple dynamo models

Observations show that the photospheric solar magnetic dipole usually does not vanish during the reversal of the solar magnetic field, which occurs in each solar cycle. In contrast, mean-field solar dynamo models predict that the dipole field does become zero. In a recent paper Moss et al. (2013) suggested that this contradiction can be explained as a large-scale manifestation of small-scale magnetic fluctuations of the surface poloidal field. Here we compare this interpretation with WSO (Wilcox Solar Observatory) photospheric magnetic field data in order to determine the amplitude of magnetic fluctuations required to explain the phenomenon and to compare the results with predictions from a simple dynamo model which takes these fluctuations into account. We demonstrate that the WSO data concerning the magnetic dipole reversals are very similar to the predictions of our very simple solar dynamo model, which includes both mean magnetic field and fluctuations. The ratio between the rms value of the magnetic fluctuations and the mean field is estimated to be about 2, in reasonable agreement with estimates from sunspot data. The reversal epoch, during which the fluctuating contribution to the dipole is larger than that from the mean field, is about 4 months. The memory time of the fluctuations is about 2 months. Observations demonstrate that the rms of the magnetic fluctuations is strongly modulated by the phase of the solar cycle. This gives additional support to the concept that the solar magnetic field is generated by a single dynamo mechanism rather than also by independent small-scale dynamo action. A suggestion of a weak nonaxsymmetric magnetic field of a fluctuating nature arises from the analysis, with a lifetime of about 1 year.Comment: 9 pages, 10 figures, accepted versio

Structure and evolution of the large scale solar and heliospheric magnetic fields

Structure and evolution of large scale photospheric and coronal magnetic fields in the interval 1976-1983 were studied using observations from the Stanford Solar Observatory and a potential field model. The solar wind in the heliosphere is organized into large regions in which the magnetic field has a componenet either toward or away from the sun. The model predicts the location of the current sheet separating these regions. Near solar minimum, in 1976, the current sheet lay within a few degrees of the solar equator having two extensions north and south of the equator. Soon after minimum the latitudinal extent began to increase. The sheet reached to at least 50 deg from 1978 through 1983. The complex structure near maximum occasionally included multiple current sheets. Large scale structures persist for up to two years during the entire interval. To minimize errors in determining the structure of the heliospheric field particular attention was paid to decreasing the distorting effects of rapid field evolution, finding the optimum source surface radius, determining the correction to the sun's polar field, and handling missing data. The predicted structure agrees with direct interplanetary field measurements taken near the ecliptic and with coronameter and interplanetary scintillation measurements which infer the three dimensional interplanetary magnetic structure. During most of the solar cycle the heliospheric field cannot be adequately described as a dipole

Just For The Hell Of It: A Comparison Of Two Taboo-Term Constructions

The two English constructions exemplified in Let\u27s get the hell out of here (type G) and They beat the hell out of him (type B) differ both syntactically and semantically, but in both the taboo expression has the force of an intensifier. History (through a corpus investigation) reveals that the B-construction started as a literal exorcism (beat the devil out of someone), where the hell substituted for the devil, and semantic bleaching ultimately made the literal sense give way to simple emphasis, with any taboo term jumping in. The G-construction may have developed simultaneously, always as an intensifier--or, perhaps, later, on analogy with B. Our analysis suggests that the use of taboo terms as intensifies spread from wh-constructions to these constructions and, finally, to degree intensifier constructions. These two uses of taboo terms as intensifies are best characterized in terms of constructions and thus offer evidence against theories lacking any notion of constructions as basic building blocks. Further, they give us information about language change: a pragmatically unified but semantically disparate class of expressions (namely, taboo terms) can extend its distribution in parallel

How much more can sunspots tell us about the solar dynamo?

Sunspot observations inspired solar dynamo theory and continue to do so. Simply counting them established the sunspot cycle and its period. Latitudinal distributions introduced the tough constraint that the source of sunspots moves equator-ward as the cycle progresses. Observations of Hale's polarity law mandated hemispheric asymmetry. How much more can sunspots tell us about the solar dynamo? We draw attention to a few outstanding questions raised by inherent sunspot properties. Namely, how to explain sunspot rotation rates, the incoherence of follower spots, the longitudinal spacing of sunspot groups, and brightness trends within a given sunspot cycle. After reviewing the first several topics, we then present new results on the brightness of sunspots in Cycle 24 as observed with the Helioseismic Magnetic Imager (HMI). We compare these results to the sunspot brightness observed in Cycle 23 with the Michelson Doppler Imager (MDI). Next, we compare the minimum intensities of five sunspots simultaneously observed by the Hinode Solar Optical Telescope Spectropolarimeter (SOT-SP) and HMI to verify that the minimum brightness of sunspot umbrae correlates well to the maximum field strength. We then examine 90 and 52 sunspots in the north and south hemisphere, respectively, from 2010 - 2012. Finally, we conclude that the average maximum field strengths of umbra 40 Carrington Rotations into Cycle 24 are 2690 Gauss, virtually indistinguishable from the 2660 Gauss value observed at a similar time in Cycle 23 with MDI

The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Optimization of the Spectral Line Inversion Code

The Very Fast Inversion of the Stokes Vector (VFISV) is a Milne-Eddington spectral line inversion code used to determine the magnetic and thermodynamic parameters of the solar photosphere from observations of the Stokes vector in the 6173 A Fe I line by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We report on the modifications made to the original VFISV inversion code in order to optimize its operation within the HMI data pipeline and provide the smoothest solution in active regions. The changes either sped up the computation or reduced the frequency with which the algorithm failed to converge to a satisfactory solution. Additionally, coding bugs which were detected and fixed in the original VFISV release, are reported here.Comment: Accepted for publication in Solar Physic